The following are some issues that exist with the power saving techniques employed in many current wireless systems, such as WiMAX or IEEE 802.16e systems.
In WiMAX and IEEE 802.16e systems, a mobile station may be placed in a power conserving state, such as sleep state or idle state. These states typically include windows/intervals of reduced communication ability to conserve power. However, in these systems, a mobile station (MS) in sleep state or idle state will miss, for example, the downlink channel descriptor/uplink channel descriptor (DCD/UCD) transmissions if it is in its sleep window (sleep state) or paging unavailable interval (idle state).
Typically in these systems, when an MS wakes up in a listening window (sleep state) or paging listening interval (idle state), if a system configuration change count has changed, indicating that the system configuration information currently stored by the mobile device is different than that currently in effect, the MS has to stay awake until proper reception of the next DCD/UCD transmission from a base station (BS).
The above issues can potentially incur unnecessary power consumption. In addition, they can potentially cause unnecessary delay for sleep-to-active and idle-to-active transition.
In some of these systems, the sleep window or paging unavailable interval can be quite large. During this time, the BS cannot transmit data to the MS and cannot trigger the MS to perform state transition to active state. To reduce state transition latency, the sleep window or paging unavailable interval can be set to a small value, however, at the expense of increased power consumption.
Also, in these systems there are typically a number of broadcast messages sent by the BS, e.g. DCD/UCD, MOB_NBR-ADV, MOB_SLP-RSP, MOB_PAG-ADV, FPC etc. However, some of this information may only be relevant to MSs in certain states (sleep, idle, normal), e.g. MOB_PAG-ADV is only relevant to MSs in idle state. However, in these systems the MS typically has no way to discern between messages before decoding them and therefore may have to decode all of the traffic bursts with Broadcast connection identifier (CID), thereby incurring unnecessary processing and power consumption at the MS.